The present invention generally relates to an image processing apparatus and methods, and more particularly, to an improvement in a process of correcting a background image. The present invention is suitably applicable to an image processing apparatus such as a digital copying machine, a facsimile machine or an image reading apparatus.
Recently, a variety of image processing directed to forming a reproduced image on a clear reproduced background image has been proposed. Japanese Laid-Open Patent Application No. 57-53179 discloses an MTF correction procedure using a highpass filter. However, in the proposed MTF correction procedure, a high-frequency noise such as an unevenness in density of background is emphasized. Thus, a reproduced background image is contaminated and a noisy reproduced image may be formed.
Japanese Laid-Open Patent Application No. 55-58670 discloses a procedure for eliminating a noise component in an original image by a gradation correction. However, the proposed procedure is complex. In case where the proposed procedure is realized by hardware, the scale thereof is very large and is thus very expensive. Alternatively if the proposed procedure is realized by software, it takes a long time to execute the procedure, and thus the proposed procedure is not suitable for a device which needs high-speed real time processing, such as a digital copying machine.
Japanese Laid-Open Patent Application No. 60-263576 discloses a process of sharpening or smoothing an image signal to be recorded to thereby correct a reproduced image. However, it is very difficult to eliminate a background contamination from a readout image while suppressing the occurrence of a deformation of the readout image. In addition, the proposed process needs a complex calculation procedure.